I think it's a bug (Android v35.2, endless). At the end, a golem died and disappeared.
Thanks for letting me know.
I'm afraid there's no way for me to reproduce this at the moment, but I will keep an eye out for it.
If it ever happens in the desktop build you can undo a few times and press M to save a screenshot (which will have the level in it that I can load to reproduce the issue). Unfortunately, saving to the Android file system isn't supported by the libraries I use.